1. Field of the Invention
The invention relates to a seal structure for a part which includes an interval between a first member and a second member sandwiching a gasket, and in which a third member is disposed to face the first member and second member via a liquid sealing material, a chain case on which this seal structure can be used, and a seal structure formation method.
2. Description of the Related Art
A seal structure including an interval between two mated members, in which a third member is disposed via a liquid sealing material, or in other words a seal structure for a so-called three surface mating portion, is used as a seal structure for a chain case (also referred to as a chain cover) of an internal combustion engine (see Japanese Patent Application Publication No. 2004-68672 (JP-A-2004-68672) and Japanese Patent Application Publication No. 2002-257241 (JP-A-2002-257241), for example). The chain case is bolted to the internal combustion engine side and sealed to an internal combustion engine side wall surface via the liquid sealing material (also referred to as liquid packing or a liquid gasket).
However, in this type of seal structure, the liquid sealing material must extend to the internal combustion engine side, or in this case to an end portion of a gasket sandwiched between a cylinder head and a cylinder block. When the liquid sealing material does not extend to and seal the end portion of the gasket, lubricating oil in the chain case passes between the cylinder head and the cylinder block through a gap between the gasket end portion and the liquid sealing material and leaks to the outside.
In JP-A-2004-68672, to prevent lubricating oil leakage from the interior of the chain case, an angle formed by the cylinder head and the cylinder block is chamfered to form a space into which the liquid sealing material is charged, and the end portion of the gasket is disposed in this space to ensure that a gap is not formed between the gasket and the liquid sealing material. Furthermore, a groove is formed on the chain case side so that even when the end portion of the gasket projects to the chain case side, a seal can be formed by the liquid sealing material.
In JP-A-2002-257241, a recessed portion is formed on the chain case side around the interval between the cylinder head and the cylinder block such that pressure is applied to the liquid sealing material entering the interior of the recessed portion during fastening of the chain case, and as a result, the liquid sealing material is pushed into a space formed by chamfering in a similar manner to JP-A-2004-68672. Thus, a gap is not formed between the gasket end portion and the liquid sealing material.
However, in both JP-A-2004-68672 and JP-A-2002-257241, when the chain case is fastened to the internal combustion engine side such that the liquid sealing material receives pressure between the chain case and the internal combustion engine, the liquid sealing material flows in an opening direction of the groove-form space or the groove-form recessed portion, or in other words a horizontal left-right direction (a width direction of the gasket disposal interval). Hence, the liquid sealing material does not infiltrate the interval between the cylinder head and the cylinder block sufficiently, and as a result, the liquid sealing material does not flow sufficiently to the position in which sealing is required.